Process and apparatus for the separation of suspensions



June 18, 1968 s. JACKERING PROCESS AND APPARATUS FOR THE SEPARATION OFSUSPENSIONS Filed June 17, 1963 G --GASES DRY FPRODUCT Fig. 2

COLD AIR, ETC.

INVENTOR. auwrm uA'c/rzme United States Patent 3,338,733 PROCESS ANDAPPARATUS FOR THE SEPARATION OF SUSPENSIONS Giinter Jackering,Vorsterhauserweg 22d, Hamrn in Westphalia, Germany Filed June 17, 1963,Ser. No. 288,213 1 Claim. (Cl. 159-4) ABSTRACT 0F THE DISCLOSURE Forseparating solid particles suspended in a liquid, the process providesfor breaking up the suspension in a gaseous vortex into solid particleswith liquid film adhering thereto, and flash heating the particles toevap rate the film therefrom; the apparatus provides a closed containerthat surrounds a bladed rotor generating the vortices, inlets andoutlets for the gases and the suspending liquid, and for withdrawing thegases and solid particles.

The present invention relates to the separation of suspensionsconsisting of solid particles in a liquid, more particularly, to themechanical separation of the solid particles from the liquid and theevaporation of liquid films adhering to the particles so as to obtaindry solid particles.

In many industrial processes suspensions of solids in liquids areobtained which may include either the desired end product or variousby-products. The utility of such suspensions often depends on theeconomic feasibility of separating the liquid and solid phases. For thispurpose, it has been customary to use various evaporation processescarried out either at atmospheric or sub-atmospheric pressures. However,these evaporation procedures were inherently disadvantageous since theevaporators necessary for this purpose were necessarily of a largecapacity to provide a yield sufiicient for industrial processes.Further, such evaporators required suitable auxiliary apparatus. Thiswas especially true of spraying towers wherein the exhausted air had atemperature of about 120l80 C.

Rotary drum dryers which operated on the thin film principle were alsoemployed but had the disadvantage of limited use particularly in thefood production industry because of the tendency for deposits andaccumulations to be formed within the dryers and the various temperaturefluctuations encountered in such dryers. In order that variousnutritional values of foods were not impaired in the production offoodstuffs, it was necessary that such foodstuffs be heated for onlylimited periods of time and below certain temperatures.

Attempts have also been made to use heated mills for dryingmoisture-containing foodstuffs but such suspensions could not besuccessfully dried in tubular, hammer, or impact mills because of thetendency to gum up and form deposits within the mills.

It is therefore the principal object of the present invention to providea novel and improved process and apparatus for the separation andremoval of solids suspended in liquids.

It is a further object of the present invention to provide a process andapparatus for the mechanical separation of solids suspended in liquidswherein the apparatus occupies a minimum of space and the process can becarried out in a short period of time.

After intensive investigation, it was found that suspensions containingup to 60% liquid can be dried in a single treatment if the suspension isfirst atomized into tiny fog-like droplets and then followed by suddenand abrupt flash heating to dry the particles by evaporation of liquidsadhering thereto. Such a process could be car- 3,388,733 Patented June18, 1968 ried out, although not very efficiently, by atomization of thesuspension in a spraying tower.

The present invention, however, provides for carrying out this processin a minimum of space by utilizing a high speed vortex separator whereinvortices are formed in the atmosphere within the separator and thevortices are subjected to continued impulse changes in direction andmagnitude. Such a vortex will separate the fine solid particles from thesuspension because of the unequal distributions of energy throughout. Bydelivering heat to this vortex, after the particles have been separated,the particles will undergo sudden and abrupt flash heating. Since thisthermal energy will act from all sides upon spherical microscopicparticles the heat will contact the solid particles in these globules ina minimum of time and with unexpected results. These results will beproduced by flat vortices following rapidly after one another inconsequence of the rotation of the scoop blades within the internallyribbed stator. In one form of this invention the rotor operates in aspace 750 mm. in diameter while the ribs and the spaces between themmeasure 6 mm. If the rotor of such an apparatus is given 2100revolutions per minute, about 82,000 flat vortices per minute will beproduced.

During the separation process, the solid particles entrained in thevortex will carry most of the liquid in the form of films adhering tothe particles. These relatively thin liquid films are quickly penetratedby the hot gases entering into the vortex and the films will be quicklyevaporated. As a result, dried solid particles are produced.

Other objects and advantages of the present invention will be readilyapparent upon reference to the accompanying description when taken inconjunction with the following drawings wherein:

FIGURE 1 is a schematic vertical sectional view that illustratesdiagrammatically one form of apparatus which can be used for carryingout the present process;

FIGURE 2 is a Schematic sectional view taken along the line IIII ofFIGURE 1;

FIGURE 3 shows schematically a solid particle after it has beenseparated from the suspension and having an adhering film of liquid;

FIGURE 4 shows schematically the solid particle after it has been driedand the liquid film has been evaporated;

FIGURE 5 shows schematically a solid particle sur rounded by a film ofmoisture and a coating material;

FIGURE 6 shows the same particle of FIGURE 5 after being dried; and

FIGURE 7 illustrates the same dried solid particle of FIGURE 6, buthaving a film of fat adhering thereto.

Referring now to the drawings wherein like reference symbols indicatethe same parts throughout the various views, FIGURE 1 shows one form ofan apparatus for carrying out the process of the present invention. Thisapparatus comprises a closed cylindrical container 1 with the centrallongitudinal axis thereof being positioned vertically. Mounted withinthe container 1 and rotatable about the central longitudinal axis is arotor 2 having a plurality of scoop blades 3 on the ends of radiallyextending arms 4.

If the substance being processed is very viscous the inner surface ofthe container 1 is smooth. But if the substance is not very viscous theinner surface can be provided with either longitudinal or bothlongitudinal and circumferential ribs, as indicated at 5. The innersurface of this container can also be provided with a rifiled surface.

A liquid suspension which is to be processed is shown in a tank 6 whichis connected through the pump 7 to the bottom of the container 1, at 8.The rotor 2 is ro- 3 tated by an electric motor 9 mounted on the top ofthe container 1.

The bottom of the container 1, indicated at 10, is provided with aplurality of openings 11 through which heated or cooled gases, such asair, are introduced.

At the upper end of the container 1 there is provided an exhaust conduit12 through which gases and dried particles are removed from thecontainer and are flowed through a line 13 to a centrifugal separator14. Other forms of separators such as filters may also be used forseparating the dried particles from the gases. The separator gases arethen removed from the separator through the exhaust line 15 and thedried particles are removed from the bottom of the separator at 16. Thedried products may either be partially removed at F or may berecirculated through the line 17 into the suspension contained in thetank 6.

A branched conduit 18 is provided which connects to the suspensiondelivery line 8. Additional materials may be added through this branchconduit line including heated gases.

The second branch conduit 19 connects to the exhaust conduit 12 forintroducing cold air or other material to the solid particles as theyleave with the gases.

In order to carry out the process of the present invention, heated airat a temperature of l00250 C. is introduced into the container 1 throughthe openings 11 in the bottom of the container, or may be introducedthrough the branch conduit 18 together with the suspension beingdelivered to the bottom of the container. The

rapid rotation of the rotor creates a plurality of vortices in theatmosphere Within the container. The liquid suspension is thenintroduced in the bottom or sides of the container under the action ofthe pump 7. The suspension is immediately vigorously agitated and is subdivided into small droplets which comprise the solid particles havingliquid films adhering thereto. These solid particles are then contactedby the heated gases within the vortices and the liquid films areevaporated and the particles dried in 1 to 1.5 seconds.

The gases are then withdrawn through the exhaust conduit 12 at atemperature of about 60 C. although the exhaust gases may range from-100 C. These exhaust gases have entrained therein the dried solidparticles and are flowed through the line 13 into the centrifugalseparator 14 wherein the separated gases are discharged at 15 and thedried solid particles discharged at 16.

In this manner, suspensions containing of liquid can have their liquidcontent reduced to about 10% so that even with relatively smallapparatus the yield of this process can be measured in tons and theprocess is feasible for industrial purposes.

When the suspension is difficult to process or the liquid content ismore than 60%, a portion of the dried solids can be returned through theline 17 to be recirculated into the suspension in the tank 6 so as tomaintain the required proportion of solids to liquids in the suspension.

The process of the present invention has been particularly useful forthe preparation of foodstuffs from brewers yeast wherein the processessentially comprises the mixing of soybeans and perhaps dried skim milkwith sour whey to produce the foodstuff. Soya meal contains valuableproteins in different forms of which finely disintegrated forms areparticularly valuable in such a foodstuff. In this invention thedisintegration of the protein is advantageously promoted by the suddenand abrupt flash heating to which these droplets are subjected.

During the application of this process it has also been determined thatthose temperatures which are usually injurious to vitamins can berendered harmless if the time during which particles containing thevitamins is greatly reduced and the interiors of the solid particles areprotected from the heat by adherent films of moisture. It has also beenadvantageous to coat the fine globules immediately after they have beenseparated from the suspension with a relatively dry material such aswheat flour which has been sufficiently disintegrated by the vortices toenable the dry material to cling to the globules and thus assist in thedrying process. Further, it has been found that a gas permeable coatingof such added materials such as illustrated at b in FIGURE 6 will alsoprotect the solids in the droplet.

In order to disclose several specific embodiments of the process of thepresent invention, several operating examples will be set forth indetail. It is to be understood that these examples are not limitative ofthe invention, but are only illustrative thereof.

Example 1 Liquid yeast containing about water and 20% solids is mixedwith relatively dry wheat flour paste in an agitated air atmospherehaving a temperature of 250 C. in the container so as to produce in thelimited time of mixing and with preservation of the vitamin con tent adried product of only 210% water which will be sufiicient to stabilizethe vitamins for a relatively long period of time. The vaporizingtemperature was 80 C. and liquid was removed at a rate of 200 kg/honr.

This unexpected result can be attributed to the existence of aircurrents of high kinetic energy and rapidly changing velocities in thevortices formed in the closed container. In these vortices individualyeast particles are coated with the added materials in such a manner soas to protect the yeast against the heat on the exterior thereof. Thecoating thus serves as heat insulation. The yeast protein during thisprocess is so effectively protected that on the one hand there will beno vitamin losses and on the other hand the preservation of the entiremixture will be assured.

It has been found that a particularly valuable product can be obtainedif the mixture being exhausted from the closed container is cooled bycold air introduced at 19 together with an admixture of fat. The fat isbest added to the insulating film on the yeast particles after they havebeen contacted by the cold air and should be in such an amount that eachparticle of yeast, as shown in FIG- URE 7, will have, a porousinsulating film b which will have absorbed thereon a layer of fat 0 butwithout the formulation of any globules of fat. The added animal orvegetable fat is securely attached to the surfaces of the porousparticles and thus ensures the preservation of the thin film of water onthe surface of the particle because the covering of fat will prevent theabsorption of additional moisture. It would also be possible tointroduce the cold air and fat into the upper portion of the container 1through the cylindrical walls thereof.

Example 2 During the preparation of starch paste from wheat flour thepaste is obtained in a moist condition. The paste possesses all of itsoriginal properties and particularly its ability to rise during baking.

Such a paste can be utilized in the two following ways:

(1) For the production of glutamic acid and in the sauce industry. Forthis purpose the moist paste is dried in rotating drums with loss of itsoriginal properties. This, however, is of no consequence for itsintendedpurposes.

(2) For improving the baking characteristics of wheat flour.

Since the original properties of the paste must be completely preservedwhen used for purpose (2), the paste must always be used in a moistenedcondition. This has the disadvantage of necessitating its immediate'usebe-' expensive.

In several applications, particularly in Australia and England, suchpastes have been dried by rotary dryers but not without some alterationof their original properties. For the preservation of the originalproperties, the drying of the paste must be very carefully carried out.This is accomplished in the present process although the temperaturesemployed in this process are far above those generally consideredpermissible for the drying of such pastes. Previously, temperaturesbetween l00-120 C. have been used in the continuous process.

In order to facilitate the introduction into the apparatus of theoriginal 70% liquid content paste obtained by the conversion of wheatflour into starch, dried paste was added thereto until the mixtureacquired a moist, crumbly consistency. The initial proportions were 13kg. dry paste to 12 kg. wet paste. The dry paste was then obtained andreturned in such amounts to the original tank that a moist, crumblymaterial is obtained. The final product had an 80% protein content and aliquid content of only as compared to a liquid content of 35% at thebeginning of the treatment.

It is therefore apparent that the present invention disclose a processfor the separation of liquid suspensions without destroying any of theinherent properties therein. The process has a particular application inthe manufacture of food stuffs where the retention of all nutritionalvalues of the ingredients is a prime objective. The apparatus disclosedherein is only one form for carrying out this process, but has theadvantage of being compact, occupying a minimum of space, and producinga sufficiently high yield so that the process is feasible for industry.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions and,accordingly, it is desired to comprehend such modifications within thisinvention as may fall within the scope of the appended claim.

What is claimed is:

1. In a process for the separation and removal of solid particlessuspended in a liquid, the steps comprising introducing heated gases ata temperature of from 100 C. to 250 C. into a closed container, beatingportions of the atmosphere in the closed container to form a pluralityof vortices in the heated gas therein, introducing a suspension of solidparticles in a liquid into the closed container so that the suspensionis separated into at least solid particles with films of liquid adheringthereto by the forces generated in the vortices formed in the heatedgases, and withdrawing the gases and dried particles with said gasesbeing at a temperature of from C. to C. the separated solid particlesbeing subjected to flash heating from heated gases for from 1 to 1.5seconds to evaporate the liquid films therefrom.

References Cited UNITED STATES PATENTS 2,333,333 11/1943 Peebles et al.159-48 X 1,964,858 7/1934 Peebles 159-48 X 2,542,270 2/ 1951 Zahm 159-62,974,725 3/1961 Samesreuther et al. 159-6 3,067,812 12/1962 Latinen etal. 159-6 1,795,495 3/1931 Lavett 210-374 2,560,807 7/1951 Lobo 23-483,053,615 9/1962 Steinert 159-48 3,126,289 3/1964 Spilman et al 159-483,275,420 9/ 1966 Tchouriline-Kissileff 159-48 FOREIGN PATENTS 25,6341897 Great Britain.

11,064 1903 Great Britain.

24,408 1903 Great Britain.

NORMAN YUDKOFF, Primary Examiner.

J. SOFER, Assistant Examiner.

